Process for bleaching organic textile materials with alkali metal chlorites containing an ester which controls the evolution of chlorine dioxide



GLUCE-Ci PROCESS FOR BLEACHING ORGANIC TEXTILE Pierre Mosse, Lyon, France, assignor to Societe Rhodiaceta, Paris, France No Drawing. Application February 21, 1955 Serial No. 489,735

Claims priority, application France February 23, 1954 3 Claims. (Cl. 8-108) The present invention relates to the bleaching of textile materials by means of chlorite solutions, and it has particular relation to improvements in carrying out this bleaching process.

It has been known that various textile materials can be advantageously bleached by treating them with hot chlorite solutions, to which an acid or an acidic salt is added. However, these procedures have the disadvantage that they cause strong evolution into the atmosphere of dioxide of chlorine, which is extremely harmful and necessitates very specific precautions. Furthermore, evolution of dioxide of chlorine weakens the bleaching power of the bath, because an essential part of the active material is thereby lost into the surrounding atmosphere.

It has been suggested to reduce these disadvantages by incorporating in non-acid chlorite solutions an organic compound which is oxidizable in acid, under the action of chlorite. These attempts have not been successful because although they may improve the bleaching effect, they do not prevent evolution of dioxide of chlorine and its escape into the atmosphere.

In view of the fact that the contents in dioxide of chlorine of a work-room should not exceed l/ 1,000,000 (Handbook of Dangerous Materials, page 94) without the risk of harmful physiological effects, this type of bleaching which gives remarkable results, has found only very limited practical use.

The main object of the present invention is the elimination of these disadvantages. Another object of the invention consists in providing a novel process for bleaching by means of salts of chlorous acid, without the harmful evolution of dioxide of chlorine into the atmosphere.

According to the process of the present invention, the textile materials to be bleached are treated in hot solutions of chlorite containing at least one non-oxidizable ester of an organic acid, without the addition of acids or acidic salts or compounds which, by oxidation, yield acids.

It has been found that by treating textile materials under the conditions described hereinafter, a bleaching effect is obtained which is comparable to the bleaching effect obtainable with the addition of acid, in which, however, no perceptible evolution of dioxide of chlorine occurs. It has been further found that such bleaching baths can be preserved at ordinary room temperatures, e. g. -25 C., and can be reheated for repeated use without losing their activity, so that used baths can be preserved and re-utilized after the addition of the amount of chlorite, which has been consumed in the preceding bleaching operation and after addition of a corresponding amount of a non-oxidizable ester of an organic acid.

In carrying out the process of the invention, the ester and its amount are selected in dependence on the desired extent of bleaching and the material to be bleached. 70

Thereby, a simple, complex or internal ester of a monoor dicarboxylic acid, which may be aliphatic, cyclanic or SEARCH ROOM KIT aromatic, can be used, such as ethyl acetate, formates or acetates of glycol or glycerol, ethyl lactate or tartrate, ethyl phthalate, -butyrolactone and the like.

The cation of the chlorite used is irrelevant and, for example, an alkali chlorite or alkaline-earth metal chlorite can be used.

The proportion between chlorite and the ester should be selected in such manner that the pH of the bath is preferably in the range between 8 and 6, at the beginmng.

The process of the invention can be applied to all kinds of textile materials, which may be natural, artificial or synthetic, especially textile materials consisting of cellulose, cellulose derivatives, polyamides, polyesters and acrylic or vinylic polymers.

The concentrations of chlorite and of the ester and the temperature of bleaching can be essentially varied, depending on the material to be bleached and can be easily determined by simple tests. However, his of particular advantage to use solutions containing 0.5- grams of the chlorite per liter and 01-20 grams of ester per liter and to use 10300 grams of chlorite per kilogram of the material to be bleached. It will be understood that any non-acidic material, particularly anti-rust or anticorrosion agents, such as nitrates, fluorides and the like can be incorporated in the baths. Bleaching is continued until the desired effect is obtained, i. e. usually for about to 180 minutes.

Bleaching according to the invention can be carried out at any desired temperature. For reasons of economy and convenience, it is preferred to use temperatures in the range of 40 to 150 0, although these limits can be considerably exceeded. However, it has been found advisable not to exceed, in general, 98 C. when operating in an open vessel, in order to obtain higher efficiency of the treatment.

The following examples illustrate some embodiments of the invention, to which the invention is not limited.

Example I 2 kg. of polyacrylonitrile fiber are immersed in 100 liters of a solution containing:

3 grams per liter of sodium chlorite and 1 gram per liter of ethyl lactate.

The solution is gradually heated to 100 C. and this temperature is maintained for one hour. The fiber is then rinsed, wringed and dried. It has a very pure white appearance. The pH of the bath is always equal to at least 6.5 and no evolution of dioxide of chlorine can be observed in the neighborhood of the bleaching vessel. By the addition of 2 grams of sodium nitrate per liter, any corrosion of non-oxidizable steel is prevented.

Example II 3 kg. of a polyamide fiber is immersed in liters of a solution containing:

3 grams per liter of sodium chlorite and 2 grams per liter of ethyl acetate.

The bath is gradually heated in an autoclave to 130 C. within an hour and this temperature is maintained for minutes. The fiber is very well bleached without the evolution of dioxide of chlorine.

Example III 0.500 kg. of cellulose acetate fiber are immersed in 25 liters of a solution containing:

4 grams per liter of sodium chlorite and 0.2 gram per liter of ethyl lactate.

By heating to 70 C. for an hour, a very pure white 3 grams per liter of sodium chlorite and 2 grams per liter of y-butyrolactone.

The resulting fiber is very well bleached without the evolution of dioxide of chlorine.

Example V 2 kg. of glycol polyterephthalate fiber are immersed for 1 /2 hours at 98 C. in 50 liters of a solution containing:

2 grams per liter of potassium chlorite and 15 grams per liter of glycerol monoacetate.

Without the evolution of chlorine, a very white fiber 1s obtamed.

Example VI 2 kg. of cotton fiber are immersed during 1 hour at 96 C. in 30 liters of a solution containing:

15 grams per liter of potassium chlorite and 1 cm. per liter of butyl phthalate.

The fiber thus obtained is very well bleached and no evolution of dioxide of chlorine takes place.

Example VII 3 kg. of glycol polyterephthalate fiber are immersed for 1 hour at 96 C. in 75 liters of a solution containing:

2 grams per liter of sodium chlorite and 15 grams per liter of ethyl tartrate.

The resulting fiber is very well bleached and no evolution of dioxide of chlorine takes place.

What is claimed is:

1. A process for bleaching organic textile materials, said process comprising bleaching said materials in an aqueous solution of an alkali metal salt of chlorous acid having a temperature of from to C., in which is dissolved an ester selected-from the group consisting of ethyl acetate, glycol formate, glycerol formate, glycol acetates, glycerol acetates, ethyl lactate, ethyl tartrate, ethyl phthalate and -butyrolactone, the solution being free from acids, acidic salts and compounds oxidizable to yield acids, said solution containing 0.1 to 20 grams of the ester per liter and the chlorite and ester being initially in the proportion to give said solution a pH between 8 and 6.

2. A process according to claim 1, in which the aqueous solution contains from 0.5 to 25 grams per liter of the chlorous acid salt.

3. A process according to claim 1, in which the aqueous solution contains 10-300 grams of the chlorous acid salt per kg. of the material to be bleached.

References Cited in the file of this patent UNITED STATES PATENTS 2,482,891 Aston Sept. 27, 1949 FOREIGN PATENTS 5,296 Great Britain of 1905 399,319 Great Britain Oct. 5, 1933 OTHER REFERENCES American Dyestuif Reporter, Aug. 22, 1938, p. 476. 

1. A PROCESS FOR BLEACHING ORGANIC TEXTILE MATERIALS, SAID PROCESS COMPRISING BLEACHING SAID MATERIALS IN AN AQUEOUS SOSLUTION OF AN ALKALI METAL SALT OF CHLOROUS ACID HAVING A TEMPERATURE OF FROM 40* TO 150*C., IN WHICH IS DISSOLVED AN ESTER SELECTED FROM THE GROUP CONSISTING OF ETHYL ACETATE, GLYCOL FORMATE, GLYCEROL FORMATE, GLYCOL ACETATES, GLYCEROL ACETATES, ETHYL LACTATER, THEYL TARTRATE, ETHYL PHTHALATE AND Y-BUTYROLACTONE, THE SOLUTION BEING FREE FROM ACIDS, ACIDIC SALTS AND COMPOUNDS OXIDIZABLE TO YIELD ACIDS, SAID SOLUTION CONTAINING 0.1 TO 20 GRAMS OF THE ESTER PR LITER AND THE CHLORITE AND ESTER BEING INITIALLY IN THE PROPORTION TO GIVE SAID SOLUTION A PH BETWEEN 8 AND
 6. 